OVERVIEW A 3D time-lapse (41)) acquisition can result in data sets which include thousands to tens of thousands of individual images. In order to deal with the sheer volume of images contained in these data sets, it was clear that a straightforward method would be needed to navigate forward and backward in time as well as up and down in focal level through the sample. This task is handled by the 4D Viewer application. Designed as a stand-alone Macintosh application written in C, the 4D Viewer makes the task of 4D navigation an easy one. After loading a Quicktime data set that was produced either by the 4D Turnaround application or the 4D Grabber software, the user can use the mouse or keyboard to play the movies backward or forward, witching events unfold as smoothly flowing animations. The user can simultaneously roarn from the top to the bottom of the sample, following events of interest. Bookmarks can be placed at various locations in 4D space providing instant access to specific events, and these bookmarks can be saved to the disk for subsequent data analysis sessions. A "Go To" function will allow the user to jump to any timepoint and focal plane they wish, and a "You are Here" function will tell the user their current location in the data set. Movies can be looped, played at a selection of speeds, played in either direction, or examined more carefully one ftame at a time. In addition to the basic task of moving through and viewing the thousands of images making up a data set, the 4D Viewer has other powerful tools in its arsenal. An editing suite allows the user to create color overlays which can highlight features of interest the in the image. Circles, squares, freehand and straight lines, text and arrows, all in a variety of colors and sizes can be used to annotate features present in the image. By manipulating these objects in subsequent frames, dynamic, color overlays which follow moving features can be created and saved to the disk. Because these overlays are put onto the image as the movie is being played and can be switched on or off, they do not affect the image information that is under them. Additionally, because they are instiuction-based rather than bitmap-based objects, they take very little disk space to store. 5000 average-sized overlays can be stored in only 9 Mb of disk space. Enhancing this very powerful annotation tool is the ability to associate hidden text boxes with each object in an overlay. By clicking a mouse on a circle that highlights a specific cell, for example, a text box can be brought up which may outline the cell's position, fate and name. One can easily see how a fully annotated and text-enhanced data set, placed onto a CD-ROM with he 4D Viewer application, would be an incredibly powerful tool either for passing on research results, or for educational purposes.various hardware components of a 4D Live Cell microscopy workstation, but does so using easy to-understand graphic user interfaces in order to reduce the learning curve for the researcher wishing to perform these types of experiments in their own labs. The software supports 6 common digitizing framegrabber cards of both the Nubus and PCI slot configuration (including the ability to take advantage of on-card frame averaging, if present), and supports four different stage drive motors. Its modular code design makes adding support for additional hardware systems very straightforward. Significant increases in collection speed were also realized with the software's optimized design. An additional advantage of the "4D Grabber" software is the ability to gather 4D data directly to compressed QuickTime movies. By taking advantage of this feature, it is possible to gather up to 15 times as many data points per given hard disk space than when using previous 4D collection systems. This collection mode also offers a very impressive savings